The Fischer-Tropsch process is known in the art to convert synthetic gas (syngas) to hydrocarbon compounds using a catalyst, such as a metal or metal oxide catalyst. Syngas is a mixture of hydrogen (H2) and carbon monoxide (CO). The hydrocarbon compounds produced by the Fischer-Tropsch process include a mixture of compounds having between one carbon atom (C1) and greater than twenty carbon atoms (C20+), such as C50 or C100 or greater. The hydrocarbon compounds include methane, other alkanes, alkenes, aliphatic alcohols, and other oxygenated hydrocarbon compounds. For some intended uses, certain hydrocarbon compounds are desired as the predominant products of the Fischer-Tropsch process. Some Fischer-Tropsch processes have been found to selectively produce C20+, C11+, C5+, or C2-4 hydrocarbon compounds, while other Fischer-Tropsch processes have been found to selectively produce methane. For instance, iron-, cobalt-, nickel-, or ruthenium-based catalysts are known in the art to produce high levels of C5+ hydrocarbon compounds with low levels of C1-4 hydrocarbon compounds.
Ethylene, propylene (also known as propene), and butylene (also known as butene) are among the alkenes produced by the Fischer-Tropsch process. Ethylene and propylene are important reagents in the petrochemical industry because they are the monomers used in the production of many plastics. Ethylene is polymerized to make low and high density polyethylene products, such as for plastic films, containers, or coatings, while propylene is used to make polypropylene, acrylonitrile, or propylene oxide. Butylene is also used in the production of plastics, such as being polymerized to make polybutylene.
Multi-step processes of forming ethylene or propylene are known in the art. In one process, syngas is converted to methanol and dimethyl ether, which are converted to ethylene and propylene. In this process, a dual-component catalyst is used that includes a metal oxide component and a molecular sieve component. The syngas is converted to methanol and dimethyl ether by the metal oxide component, and the methanol and dimethyl ether are converted to ethylene and propylene by the molecular sieve component. In another process, syngas is converted to methanol, which is converted to ethylene or propylene. While these processes produce ethylene and propylene, they require significant capital and operating costs.